A McDonald's All-American coming out of Pittsburgh's Shaler Area High School, Fortson elected to attend the University of Cincinnati where, in his three years at the school, his scoring average rose each season. As a freshman, his impact was felt immediately. In 34 games he averaged 15.1 points and 7.6 rebounds.

The next year saw it all come together for both Fortson and Cincinnati. Leading the team to an appearance in the NCAA Basketball Tournament's Elite Eight, he averaged 20.1 points and 9.6 rebounds while being named Conference USA's Player-Of-The-Year and second team NCAA All-American.

In his junior, and final, year with the Bearcats, Fortson was again named Conference USA Player-Of-The-Year, first team All-Conference and made first team NCAA All-American. After his third year with Cincinnati, Fortson declared himself eligible for the NCAA draft. He ended his college career ranked second all-time in points for the Bearcats with 1,881 (behind only Oscar Robertson's 2,973) and second in free throws (571) and free throws attempted (768).

The Milwaukee Bucks selected the 6'7 forward in the first round of the 1997 NBA draft but traded his rights, that very evening, to the Denver Nuggets. In his rookie season, Fortson saw action in 80 games and averaged 10.2 points. The next year he averaged a double-double over 56 games with 11.0 points and 11.6 rebounds.

Traded in the offseason to Boston, he missed the first 25 games with a fractured right foot and averaged 7.6 points in 55 games. Fortson was again traded after the 1999-2000 season, this time to Golden State where he was limited to only six games his first year with the Warriors due to another stress fracture in his right foot. In those first six games he had posted career-high numbers of 16.7 points and 16.3 rebounds.

Returning to health in 2001-2002, he again averaged a double-double with 11.2 points and 11.7 rebounds. The next season, his last with Golden State, the injury bug struck again and he only played in 17 games posting 3.5 ppg.

The Mavericks obtained Fortson in the offseason as part of a nine-player deal with the Warriors. Playing behind Dirk Nowitzki and Antoine Walker, he saw action in 56 games averaging 3.9 points and 4.5 rebounds in 3.9 minutes.

Dallas traded Fortson in the offseason to Seattle for Calvin Booth and Fortson played the final three seasons of his career with the Sonics. He saw the only playoff action of his career in 2004-2005, his first year with Seattle. Foot and knee problems limited him in his final season, 2006-2007, to only 14 games in which he averaged 2.9 points.